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Family
Aphididae
- This page contains pictures and information about Cowpea Aphids that we
found in the Brisbane area, Queensland, Australia.
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 - Aphid colony, body length 1-2mm
- This aphid is known as Cowpea Aphids or Cow Pea Aphids. During the
spring season on the hibiscus plants in our backyard, we find this aphid.
They are grayish-black in colour. They are one of the famous pest, although
they seem not doing much harm to our plants. Their host include those
plants in Malvaceae and Fabaceae.
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- We have three hibiscus plants in our backyard, the red, pink and yellow. The
three plants are close to each others. The aphids only attack the red hibiscus.
We can sometimes find one or two aphids on the yellow and pink plants but never
see a colony.
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- The aphids colony expanse very quickly in early spring. They
feed on young shoots and flower buds. We also found at
last five different predator species feeding on the aphids in mid spring.
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- In the above 1st photos, a new aphids colony is just started on this flower bud. Nymphs progress through five nymphal
instars stages. Checked carefully we can see five different body size. The
pale white fellows
are the newly born aphids. The light-grey ones are the 2nd instars, the dark
grey ones are the 3rd instars and the black is the 4th instars. The largest adults
are just
giving birth a new baby. It takes about one week for the new born become an adults.
From reference infromation, a female in general produce 100 nymphs in 30 days.
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- In the crowded colony, sometimes we can find a few winged adults. It is
believed that when the colony becomes two crowded, some aphids will became
winged and fly to a new location to start a new colony. In the above picture, there are two winged form adults and some other
wingless adults. Also notice that there are three empty shells with a hole on
each shell. They are the aphid body leave by parasitic wasp.
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- In the above first picture, there are three fat yellow-brown aphids, there are
parasitised by
the wasp. Notice the two on the upper side of the picture, are empty, the wasps
had come out already. Near the two dark aphid adults, there is the white shell
which is left from a ladybird larvae after moulting.
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- The above picture are taken at the same flower buds between one week. The
first picture
showing the flower buds are fully covered with aphids. But over half of the
aphids population is yellow-brown in colour and fat, i.e., they are parasitised by
the wasp. The second picture, one week later, shows most of the
yellow-brown aphids became an empty shell with a small open hole.
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Ladybirds - the Predators
- We found at least four different ladybird beetles attack the aphids at the
same time. Both ladybirds larvae and adults feed on aphids.
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- The first picture shows Variable
Ladybird larvae. The
second picture shows the Slimline Ladybird
adult, beside feeding on the aphids, is looking for a place to lay eggs. Usually
she will lay a batch of seven or eight eggs, on the bottom side of leaf.
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- Ladybird larvae feeding on aphids. The above pictures show the Yellow
Shouldered Ladybird larvae and adult.
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- The pictures show the Common Spotted Ladybirds Larvae and adult. We do not see any defence by the aphids against the predation. The aphids
seem do not know or do not care about being eaten. They did not even border to
run away from the attack. The only defence mechanism that we observed is their
growing rate. To reproduce faster than the predation is their way of survival.
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- The above pictures show some more different ladybird larvae and adult of Mealybug
Ladybird.
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Hoverfly - the aphids predator
 
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- We often see bee-like flies hovering on our hibiscus plants. They are the Hoverflies. Hoverfly larvae are the major predator of the aphids. For a large
aphid colony, we usually find a hoverfly larvae feeding at the middle. The 3rd picture
above shows a Hoverfly adult look for a place to lay eggs.
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Lacewings Larvae - the aphids predator
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- We also found this Lacewing
eggs and larvae on our hibiscus. Aphids are the major food source of
Lacewing larvae.
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Tending by Ants
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- Aphids excrete honeydew, which is a sweet
liquid that is eagerly sought by ants. On the hibiscus plant, the ants are very active at night visiting the aphids colony. The ants come
less frequently during the day time. This may indicate that the aphids give more
honey-dew at night.
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- Some ants species are known to provide some kind of protections to
aphids. As we observed, the ants species shown did not provide any
protection. They just wandering around and look for the honey-dew. They do not
care the fly larvae or ladybird larvae eating the aphids.
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- Reference:
- 1. Insects
of Australia - CSIRO, Division of Entomology, Melbourne University
Press, 2nd Edition 1991, p 453.
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